HiI find out for biodiesel about mounth ago and from then I am reading about it how to made it. My research has led me to this forum I am glad that I found this forum so I can ask many question that i have.

I read a few recipes and looked some videos on youtube but there are all diferend.

So my first question is: How do you know how much KOH to use for new oil ?Is there diference which oil is ? corn, sunflower, rapeseed ?

I have 89% clean KOH and calcute from recipes journeytoforever it goes 5.6g per literIs this true ?

This is one of my many question I have, I hope I going to find answers on this forum

Originally posted by Andrew M:The 7g/L is for pure KOH, so you would need to adjust for purity, and the base you need is about 7.5. So, that is the suggested minimum base using your chems. I use more, as much as 9 for base, since my KOH is 90% I use 10, then add my titration.

However, there is a trade-off. More catalyst gives better conversion but more soap.

Unused oil does indeed contain water, usually around the 500ppm range. There should be no need to dry unused oil before processing.

If you titrate with a 0.1% solution of the 89% KOH that you use in the process. ie make up the solution as if it were 100%. Then the titration will be self-adjusting. ie you will get a slightly higher titration value which will compensate for the 89% purity.

Thank you for your answer now i understand I also want to ask if there are any resolts for water test I make two batch befor I join this forum and bouth fail on water test. First just bland with water it won't separate just a small small layer after 1 day Second it separate in 30 min I get 3 layer: one big white second deviding third smaller layer. The layer first and third are not the same like 60:40 so I think this isn't successful.So is there are any guide that tell where did i get wrong ?

And if this helps my cooking progres:1 liter unused oil was heating and mixing at the same time to 55 C( 2dl metanol + 5,6g KOH )added slowly when oil mixing at 55 Ctotal adding was araound 35 min at constang mixing on 55 COil temperature was drifting from 54 to 56

Originally posted by SLOboy:1 liter unused oil was heating and mixing at the same time to 55 C( 2dl metanol + 5,6g KOH )added slowly when oil mixing at 55 Ctotal adding was araound 35 min at constang mixing on 55 COil temperature was drifting from 54 to 56

dl is not a normal unit of measure in the "western world" and many people on the forum will not understand what you mean.Most of us would say 200ml instead.

Temperature is not particularly critical to the outcome of the reaction other than the cooler you have the reaction the longer you need to mix.

The "usual" amount of KOH most people seem to use for the reaction is 8g+ titration.This assumes a KOH purity of about 90%. You used 5.6g KOH.You have not used enough KOH and will have achieved a lower conversion. This would be one reason you had trouble with your "shake-um up" water test

There is no hard answer to your question. Your KOH is a catalyst, so it's not consumed in the transesterification reaction. All you need is enough to get the reaction moving. I think the academic types recommend 1% by weight. Home brewers usually use as little as possible.

When you have acids in your oil, some of it will be consumed neutralizing the acids. We titrate to determine how much is going to be consumed neutralizing those acids. If you have water in your oil, some KOH will be consumed making soap. Which is why there is so much talk about getting your oil dry enough to process. Too much water, and it will consume all of your KOH making soap.

So how much 89% KOH do you need for new oil? Like Tilly said, most home brewers use 8 grams per liter.

Just a quick clarification on how we came up with the 8g KOH per litre for new Veg oil.The chemist neutral was doing some GC testing with new veg oil to determine how much NaOH/KOH was actually required to produce biodiesel that would meet the ASTM requirement for what is normally called conversion. At that time the empirical amount of NaOH most people used was 3.5g NaOH. At that time no one used KOH however the requirement was 5g KOH on JtF..

Neutral frequently performed his experiments with KOH. If I remember correctly he did this testing using KOH and then presented his findings to the forum as 5g NaOH/ 7g KOH. This assumed a purity of 100% in each instance.NaOH usually has a purity close to 100% while KOH does not.

Because most of us do not use 100% purity KOH an adjustment is required.If your KOH is 90% purity that is about 7.8g KOH per litre required and if it is 89% purity that is about 7.9g KOH per litre required. Most people seem to round it up to 8g/ litre KOH "just in case"

If you want to take the time to look through the archives, it is all there.

This message has been edited. Last edited by: Tilly, May 04, 2015 02:14 AM